#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>
#include <string.h>
#include <assert.h>

char* My_strstr(const char* pa, const char* pb)
{
	assert(pa && pb);
	while (*pa)
	{
		char* s1 = pa;
		char* s2 = pb;
		while (*s1 == *s2)
		{
			s1++;
			s2++;
			if (*s2 == '\0')
			{
				return pa;
			}
		}
		pa++;
	}
	return NULL;
}

int main()
{
	char str1[30] = "3425588767@qq.com";
	char str2[30] = "@qq.com";
	printf("%s",My_strstr(str1, str2));
	return 0;
}